Dépouillements

Dynamic modal analysis and stability of cantilever shear buildings / Aristizábal-Ochoa, Darío J. in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.735–747. Titre : Dynamic modal analysis and stability of cantilever shear buildings : Importance of moment equilibrium Type de document : texte imprimé Auteurs : Aristizábal-Ochoa, Darío J., Auteur Année de publication : 2007 Article en page(s) : pp.735–747. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Beams  Beam  columns  Buckling  Dynamic  analysis  Natural  frequency  Seismic  analysis  Shear  waves  Earthquake  engineering Résumé : The dynamic modal analysis (i.e., the natural frequencies, modes of vibration, generalized masses, and modal participation factors) and static stability (i.e., critical loads and buckling modes) of two-dimensional (2D) cantilever shear buildings with semirigid flexural restraint and lateral bracing at the base support as well as lumped masses at both ends and subjected to a linearly distributed axial load along its span are presented using an approach that fulfills both the lateral and moment equilibrium conditions along the member. The proposed model includes the simultaneous effects and couplings of shear deformations, translational and rotational inertias of all masses considered, a linearly applied axial load along the span, the shear force component induced by the applied axial force as the member deforms and the cross section rotates, and the rotational and lateral restraints at the base support. The proposed model shows that the stability and dynamic behavior of 2D cantilever shear buildings are highly sensitive to the coupling effects just mentioned, particularly in members with limited rotational restraint and lateral bracing at the base support. Analytical results indicate that except for members with a perfectly clamped base (i.e., zero rotation of the cross sections), the stability and dynamic behavior of shear buildings are governed by the flexural moment equation, rather than the second-order differential equation of transverse equilibrium or shear-wave equation. This equation is formulated in the technical literature by simply applying transverse equilibrium “ignoring” the flexural moment equilibrium equation. This causes erroneous results in the stability and dynamic analyses of shear buildings with base support that is not perfectly clamped. The proposed equations reproduce, as special cases: (1) the nonclassical vibration modes of shear buildings including the inversion of modes of vibration when higher modes cross lower modes in shear buildings with soft conditions at the base, and the phenomena of double frequencies at certain values of beam slenderness (L/r) ; and (2) the phenomena of tension buckling in shear buildings. These phenomena have been discussed recently by the writer (2005) in columns made of elastomeric materials. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2874 [...] [article] Dynamic modal analysis and stability of cantilever shear buildings : Importance of moment equilibrium [texte imprimé] / Aristizábal-Ochoa, Darío J., Auteur . - 2007 . - pp.735–747. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.735–747. Mots-clés : Beams  Beam  columns  Buckling  Dynamic  analysis  Natural  frequency  Seismic  analysis  Shear  waves  Earthquake  engineering Résumé : The dynamic modal analysis (i.e., the natural frequencies, modes of vibration, generalized masses, and modal participation factors) and static stability (i.e., critical loads and buckling modes) of two-dimensional (2D) cantilever shear buildings with semirigid flexural restraint and lateral bracing at the base support as well as lumped masses at both ends and subjected to a linearly distributed axial load along its span are presented using an approach that fulfills both the lateral and moment equilibrium conditions along the member. The proposed model includes the simultaneous effects and couplings of shear deformations, translational and rotational inertias of all masses considered, a linearly applied axial load along the span, the shear force component induced by the applied axial force as the member deforms and the cross section rotates, and the rotational and lateral restraints at the base support. The proposed model shows that the stability and dynamic behavior of 2D cantilever shear buildings are highly sensitive to the coupling effects just mentioned, particularly in members with limited rotational restraint and lateral bracing at the base support. Analytical results indicate that except for members with a perfectly clamped base (i.e., zero rotation of the cross sections), the stability and dynamic behavior of shear buildings are governed by the flexural moment equation, rather than the second-order differential equation of transverse equilibrium or shear-wave equation. This equation is formulated in the technical literature by simply applying transverse equilibrium “ignoring” the flexural moment equilibrium equation. This causes erroneous results in the stability and dynamic analyses of shear buildings with base support that is not perfectly clamped. The proposed equations reproduce, as special cases: (1) the nonclassical vibration modes of shear buildings including the inversion of modes of vibration when higher modes cross lower modes in shear buildings with soft conditions at the base, and the phenomena of double frequencies at certain values of beam slenderness (L/r) ; and (2) the phenomena of tension buckling in shear buildings. These phenomena have been discussed recently by the writer (2005) in columns made of elastomeric materials. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2874 [...]

Improved explicit method for structural dynamics / Shuenn-Yih Chang in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.748–760. Titre : Improved explicit method for structural dynamics Type de document : texte imprimé Auteurs : Shuenn-Yih Chang, Auteur Année de publication : 2007 Article en page(s) : pp.748–760. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Structural  dynamics  Elasticity  Numerical  analysis  Nonlinear  analysis Résumé : An explicit method, which simultaneously has the most promising advantages of the explicit and implicit methods, is presented. It is shown that numerical properties of the proposed explicit method are exactly the same as those of the constant average acceleration method for linear elastic systems. However, for nonlinear systems, it has unconditional stability for an instantaneous stiffness softening system and conditional stability for an instantaneous stiffness hardening system. This conditional stability property is much better than that of the Newmark explicit method. Hence, the proposed explicit method is possible to have the most important property of unconditional stability for an implicit method. On the other hand, this method can be implemented as simply as an explicit method, and hence, possesses the most important property of explicit implementation for an explicit method. Apparently, the integration of these two most important properties of explicit and implicit methods will allow the proposed explicit method to be competitive with other integration methods for structural dynamics. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2874 [...] [article] Improved explicit method for structural dynamics [texte imprimé] / Shuenn-Yih Chang, Auteur . - 2007 . - pp.748–760. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.748–760. Mots-clés : Structural  dynamics  Elasticity  Numerical  analysis  Nonlinear  analysis Résumé : An explicit method, which simultaneously has the most promising advantages of the explicit and implicit methods, is presented. It is shown that numerical properties of the proposed explicit method are exactly the same as those of the constant average acceleration method for linear elastic systems. However, for nonlinear systems, it has unconditional stability for an instantaneous stiffness softening system and conditional stability for an instantaneous stiffness hardening system. This conditional stability property is much better than that of the Newmark explicit method. Hence, the proposed explicit method is possible to have the most important property of unconditional stability for an implicit method. On the other hand, this method can be implemented as simply as an explicit method, and hence, possesses the most important property of explicit implementation for an explicit method. Apparently, the integration of these two most important properties of explicit and implicit methods will allow the proposed explicit method to be competitive with other integration methods for structural dynamics. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2874 [...]

Simulation of a 3D numerical viscous wave tank / Hau-Wei Wang in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.761–772. Titre : Simulation of a 3D numerical viscous wave tank Type de document : texte imprimé Auteurs : Hau-Wei Wang, Auteur ; Ching-Jer Huang, Auteur ; Jin Wu, Auteur Année de publication : 2007 Article en page(s) : pp.761–772. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Simulation  Water  tanks  Breakwaters  Velocity  Numerical  analysis  Three-dimensional  analysis Résumé : A numerical scheme was developed to solve the unsteady three-dimensional (3D) Navier–Stokes equations and the fully nonlinear free surface boundary conditions for simulating a 3D numerical viscous wave tank. The finite-analytic method was used to discretize the partial differential equations, and the marker-and-cell method was extended to treat the 3D free surfaces. A piston-type wave generator was incorporated in the computational domain to generate the desired incident waves. This wave tank model was applied to simulate the generation and propagation of a solitary wave in the wave tank and the diffraction of periodic waves by a semiinfinite breakwater. The computation was carried out by a PC cluster established by connecting several personal computers. The message passing interface (MPI) parallel language and MPICH software were used to write the computer code for parallel computing. High consistency between the numerical results and the theoretical solutions for the wave and velocity profiles confirms the accuracy of the proposed wave tank model. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2876 [...] [article] Simulation of a 3D numerical viscous wave tank [texte imprimé] / Hau-Wei Wang, Auteur ; Ching-Jer Huang, Auteur ; Jin Wu, Auteur . - 2007 . - pp.761–772. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.761–772. Mots-clés : Simulation  Water  tanks  Breakwaters  Velocity  Numerical  analysis  Three-dimensional  analysis Résumé : A numerical scheme was developed to solve the unsteady three-dimensional (3D) Navier–Stokes equations and the fully nonlinear free surface boundary conditions for simulating a 3D numerical viscous wave tank. The finite-analytic method was used to discretize the partial differential equations, and the marker-and-cell method was extended to treat the 3D free surfaces. A piston-type wave generator was incorporated in the computational domain to generate the desired incident waves. This wave tank model was applied to simulate the generation and propagation of a solitary wave in the wave tank and the diffraction of periodic waves by a semiinfinite breakwater. The computation was carried out by a PC cluster established by connecting several personal computers. The message passing interface (MPI) parallel language and MPICH software were used to write the computer code for parallel computing. High consistency between the numerical results and the theoretical solutions for the wave and velocity profiles confirms the accuracy of the proposed wave tank model. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2876 [...]

Karhunen–loéve expansion of stochastic processes with a modified exponential covariance kernel / Pol D. Spanos in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.773–779. Titre : Karhunen–loéve expansion of stochastic processes with a modified exponential covariance kernel Type de document : texte imprimé Auteurs : Pol D. Spanos, Auteur ; Michael Beer, Auteur ; John Red-Horse, Auteur Année de publication : 2007 Article en page(s) : pp.773–779. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Stochastic  processes  Spectral  analysis  Monte  Carlo  method  Computer  aided  simulation  Numerical  analysis Résumé : The spectral representation of stationary stochastic processes via the Karhunen-Loéve (KL) expansion is examined from a numerical efficiency perspective. Attention is focused on processes which have commonly been characterized by covariance kernels decaying exponentially versus the position/time delay variable. By introducing a slight modification in the mathematical description of this covariance kernel, the nondifferentiability at its peak is eliminated, whereas most of its advantageous properties are retained. It is shown that compared to the common exponential model, the requisite number of terms for representing the process in context with the modified kernel is significantly smaller. The effect is demonstrated by means of a specific numerical example. This is done by first determining the eigenfunctions/eigenvalues associated with the KL expansion for the modified kernel model, and by afterwards estimating the approximation errors corresponding to the two kernels considered for specific numerical values. Clearly, the enhanced computational efficiency of the KL expansion associated with the modified kernel can significantly expedite its incorporation in stochastic finite elements and other areas of stochastic mechanics. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2877 [...] [article] Karhunen–loéve expansion of stochastic processes with a modified exponential covariance kernel [texte imprimé] / Pol D. Spanos, Auteur ; Michael Beer, Auteur ; John Red-Horse, Auteur . - 2007 . - pp.773–779. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.773–779. Mots-clés : Stochastic  processes  Spectral  analysis  Monte  Carlo  method  Computer  aided  simulation  Numerical  analysis Résumé : The spectral representation of stationary stochastic processes via the Karhunen-Loéve (KL) expansion is examined from a numerical efficiency perspective. Attention is focused on processes which have commonly been characterized by covariance kernels decaying exponentially versus the position/time delay variable. By introducing a slight modification in the mathematical description of this covariance kernel, the nondifferentiability at its peak is eliminated, whereas most of its advantageous properties are retained. It is shown that compared to the common exponential model, the requisite number of terms for representing the process in context with the modified kernel is significantly smaller. The effect is demonstrated by means of a specific numerical example. This is done by first determining the eigenfunctions/eigenvalues associated with the KL expansion for the modified kernel model, and by afterwards estimating the approximation errors corresponding to the two kernels considered for specific numerical values. Clearly, the enhanced computational efficiency of the KL expansion associated with the modified kernel can significantly expedite its incorporation in stochastic finite elements and other areas of stochastic mechanics. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2877 [...]

Model selection in applied science and engineering / R. V. Field in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.780–791. Titre : Model selection in applied science and engineering : a decision-theoretic approach Type de document : texte imprimé Auteurs : R. V. Field, Auteur ; Mircea Grigoriu, Auteur Année de publication : 2007 Article en page(s) : pp.780–791. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Bayesian  analysis  Probability  Mathematical  models  System  analysis Résumé : Mathematical models are developed and used to study the properties of complex systems in just about every area of applied science and engineering. Information on the system being modeled is, in general, incomplete, so that there may be two or more models consistent with the available information. The collection of these models is called the class of candidate models. A decision-theoretic method is developed for selecting the optimal member from the collection. The optimal model depends on the available information, the class of candidate models, and the model use. The candidate models may be deterministic or random. Classical methods for model selection, including the method of maximum likelihood and Bayesian methods, are briefly reviewed. These methods ignore model use and require data to be available. In addition, examples are used to show that classical methods for model selection can be unreliable in the sense that they can deliver unsatisfactory models when data is limited. The proposed decision-theoretic method for model selection does not have these limitations. The method accounts for model use via a utility function. This feature is especially important when modeling high-risk systems where the consequences of using an inappropriate model for the system can be disastrous. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2878 [...] [article] Model selection in applied science and engineering : a decision-theoretic approach [texte imprimé] / R. V. Field, Auteur ; Mircea Grigoriu, Auteur . - 2007 . - pp.780–791. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.780–791. Mots-clés : Bayesian  analysis  Probability  Mathematical  models  System  analysis Résumé : Mathematical models are developed and used to study the properties of complex systems in just about every area of applied science and engineering. Information on the system being modeled is, in general, incomplete, so that there may be two or more models consistent with the available information. The collection of these models is called the class of candidate models. A decision-theoretic method is developed for selecting the optimal member from the collection. The optimal model depends on the available information, the class of candidate models, and the model use. The candidate models may be deterministic or random. Classical methods for model selection, including the method of maximum likelihood and Bayesian methods, are briefly reviewed. These methods ignore model use and require data to be available. In addition, examples are used to show that classical methods for model selection can be unreliable in the sense that they can deliver unsatisfactory models when data is limited. The proposed decision-theoretic method for model selection does not have these limitations. The method accounts for model use via a utility function. This feature is especially important when modeling high-risk systems where the consequences of using an inappropriate model for the system can be disastrous. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2878 [...]

Stress concentration solution for a 2D dent in an internally pressurized cylinder / Adam J. Rinehart, in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp., 792–800. Titre : Stress concentration solution for a 2D dent in an internally pressurized cylinder Type de document : texte imprimé Auteurs : Adam J. Rinehart,, Auteur ; Peter B. Keating, Auteur Année de publication : 2007 Article en page(s) : pp., 792–800. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Damage  assessment  Defects  Gas  pipelines  Oil  pipelines  Stress  concentration  Stress  analysis  Cylindrical  shells Résumé : Dent imperfections in internally pressurized shells have a stress concentration effect. In cylindrical shells under internal pressure, such as pipelines, stress concentrations associated with dent imperfections can degrade in-service performance. A new semianalytical solution is developed for the stress concentration distribution present along the two-dimensional circumferential cross section of a cylinder under internal pressure containing a local dent-like imperfection. An equivalent load approach is used. Results are compared against finite-element results. For practical application, the stress concentration factor (SCF) present at the outer surface of the dent center is derived. Parametric studies with this expression show that long dent stress concentrations are primarily influenced by the dent depth-pipe thickness and the dent depth-pipe diameter ratios. Example cases show that SCF values between 10.0 and 20.0 are possible and that even shallow dent SCFs can be above 2.0. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2879 [...] [article] Stress concentration solution for a 2D dent in an internally pressurized cylinder [texte imprimé] / Adam J. Rinehart,, Auteur ; Peter B. Keating, Auteur . - 2007 . - pp., 792–800. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp., 792–800. Mots-clés : Damage  assessment  Defects  Gas  pipelines  Oil  pipelines  Stress  concentration  Stress  analysis  Cylindrical  shells Résumé : Dent imperfections in internally pressurized shells have a stress concentration effect. In cylindrical shells under internal pressure, such as pipelines, stress concentrations associated with dent imperfections can degrade in-service performance. A new semianalytical solution is developed for the stress concentration distribution present along the two-dimensional circumferential cross section of a cylinder under internal pressure containing a local dent-like imperfection. An equivalent load approach is used. Results are compared against finite-element results. For practical application, the stress concentration factor (SCF) present at the outer surface of the dent center is derived. Parametric studies with this expression show that long dent stress concentrations are primarily influenced by the dent depth-pipe thickness and the dent depth-pipe diameter ratios. Example cases show that SCF values between 10.0 and 20.0 are possible and that even shallow dent SCFs can be above 2.0. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2879 [...]

Unified elastoplastic–viscoplastic bounding surface model of geosynthetics and its applications to geosynthetic reinforced soil-retaining wall analysis / Huabei Liu in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.801–815. Titre : Unified elastoplastic–viscoplastic bounding surface model of geosynthetics and its applications to geosynthetic reinforced soil-retaining wall analysis Type de document : texte imprimé Auteurs : Huabei Liu, Auteur ; Ling, Hoe I., Auteur Année de publication : 2007 Article en page(s) : pp.801–815. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Time  dependence  Geosynthetics  Viscoplasticity  Creep  Plasticity Résumé : The static and dynamic behaviors of reinforced soil structures are possibly subjected to the effects of creep or stress relaxation due to the time-dependent behavior of geosynthetic inclusions and backfill. To simulate the time-dependent monotonic and cyclic behavior of geosynthetics, an isothermal constitutive model is formulated within the framework of elastoplasticity–viscoplasticity. The concept of bounding surface plasticity is first utilized to formulate a time-independent cyclic model of geosynthetics. In order to capture the hardening stiffness of some polyester geosynthetics, an exponential bounding curve is used in simulating the primary loading. The time-independent version of the model was extended into an elastoplastic–viscoplastic model using overstress viscoplasticity with reference to available experimental data. The model was evaluated using creep, stress relaxation, monotonic, and cyclic loading test results obtained for different geosynthetics. It was then incorporated into a finite-element code and the static and dynamic behavior of a geosynthetic reinforced soil wall was analyzed. The analyzed results, with and without consideration to the time-dependent behavior of the reinforcements, were compared. It was demonstrated that although the end-of-construction behavior of the reinforced soil wall was less influenced by the time-dependent properties of geogrids, the long-term performance was considerably affected. The seismic response was also affected to some extent by the rate-dependent behavior of geogrids. The effects were more significant for short and/or large vertical spacing reinforcement layout. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2880 [...] [article] Unified elastoplastic–viscoplastic bounding surface model of geosynthetics and its applications to geosynthetic reinforced soil-retaining wall analysis [texte imprimé] / Huabei Liu, Auteur ; Ling, Hoe I., Auteur . - 2007 . - pp.801–815. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.801–815. Mots-clés : Time  dependence  Geosynthetics  Viscoplasticity  Creep  Plasticity Résumé : The static and dynamic behaviors of reinforced soil structures are possibly subjected to the effects of creep or stress relaxation due to the time-dependent behavior of geosynthetic inclusions and backfill. To simulate the time-dependent monotonic and cyclic behavior of geosynthetics, an isothermal constitutive model is formulated within the framework of elastoplasticity–viscoplasticity. The concept of bounding surface plasticity is first utilized to formulate a time-independent cyclic model of geosynthetics. In order to capture the hardening stiffness of some polyester geosynthetics, an exponential bounding curve is used in simulating the primary loading. The time-independent version of the model was extended into an elastoplastic–viscoplastic model using overstress viscoplasticity with reference to available experimental data. The model was evaluated using creep, stress relaxation, monotonic, and cyclic loading test results obtained for different geosynthetics. It was then incorporated into a finite-element code and the static and dynamic behavior of a geosynthetic reinforced soil wall was analyzed. The analyzed results, with and without consideration to the time-dependent behavior of the reinforcements, were compared. It was demonstrated that although the end-of-construction behavior of the reinforced soil wall was less influenced by the time-dependent properties of geogrids, the long-term performance was considerably affected. The seismic response was also affected to some extent by the rate-dependent behavior of geogrids. The effects were more significant for short and/or large vertical spacing reinforcement layout. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2880 [...]

Transitional markov chain monte carlo method for bayesian model updating, model class selection, and model averaging / Jianye Ching in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.816–832. Titre : Transitional markov chain monte carlo method for bayesian model updating, model class selection, and model averaging Type de document : texte imprimé Auteurs : Jianye Ching, Auteur ; Yi-Chu Chen, Auteur Année de publication : 2007 Article en page(s) : pp.816–832. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Bayesian  analysis  Simulation  Markov  chains  Monte  Carlo  method Résumé : This paper presents a newly developed simulation-based approach for Bayesian model updating, model class selection, and model averaging called the transitional Markov chain Monte Carlo (TMCMC) approach. The idea behind TMCMC is to avoid the problem of sampling from difficult target probability density functions (PDFs) but sampling from a series of intermediate PDFs that converge to the target PDF and are easier to sample. The TMCMC approach is motivated by the adaptive Metropolis–Hastings method developed by Beck and Au in 2002 and is based on Markov chain Monte Carlo. It is shown that TMCMC is able to draw samples from some difficult PDFs (e.g., multimodal PDFs, very peaked PDFs, and PDFs with flat manifold). The TMCMC approach can also estimate evidence of the chosen probabilistic model class conditioning on the measured data, a key component for Bayesian model class selection and model averaging. Three examples are used to demonstrate the effectiveness of the TMCMC approach in Bayesian model updating, model class selection, and model averaging. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2881 [...] [article] Transitional markov chain monte carlo method for bayesian model updating, model class selection, and model averaging [texte imprimé] / Jianye Ching, Auteur ; Yi-Chu Chen, Auteur . - 2007 . - pp.816–832. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.816–832. Mots-clés : Bayesian  analysis  Simulation  Markov  chains  Monte  Carlo  method Résumé : This paper presents a newly developed simulation-based approach for Bayesian model updating, model class selection, and model averaging called the transitional Markov chain Monte Carlo (TMCMC) approach. The idea behind TMCMC is to avoid the problem of sampling from difficult target probability density functions (PDFs) but sampling from a series of intermediate PDFs that converge to the target PDF and are easier to sample. The TMCMC approach is motivated by the adaptive Metropolis–Hastings method developed by Beck and Au in 2002 and is based on Markov chain Monte Carlo. It is shown that TMCMC is able to draw samples from some difficult PDFs (e.g., multimodal PDFs, very peaked PDFs, and PDFs with flat manifold). The TMCMC approach can also estimate evidence of the chosen probabilistic model class conditioning on the measured data, a key component for Bayesian model class selection and model averaging. Three examples are used to demonstrate the effectiveness of the TMCMC approach in Bayesian model updating, model class selection, and model averaging. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2881 [...]

Closed-form fragility estimates, parameter sensitivity, and bayesian updating for RC columns / Do-Eun Choe in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.833–843. Titre : Closed-form fragility estimates, parameter sensitivity, and bayesian updating for RC columns Type de document : texte imprimé Auteurs : Do-Eun Choe, Auteur ; Gardoni, Paolo, Auteur ; Rosowsky, David, Auteur Année de publication : 2007 Article en page(s) : pp.833–843. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Bridges  Concrete  columns  Shear  Deformation  Bayesian  analysis  Sensitivity  analysis  Probabilistic  models  Parameters Résumé : Reinforced concrete (RC) columns are the most critical components in bridges under seismic excitation. In this paper, a simple closed-form formulation to estimate the fragility of RC columns is developed. The formulation is used to estimate the conditional probability of failure of an example column for given shear and deformation demands. The estimated fragilities are as accurate as more sophisticated estimates (i.e., predictive fragilities) and do not require any reliability software. A sensitivity analysis is carried out to identify to which parameter(s) the reliability of the example column is most sensitive. The closed-form formulation uses probabilistic capacity models. A Bayesian procedure is presented to update existing probabilistic models with new data. The model updating process can incorporate different types of information, including laboratory test data, field observations, and subjective engineering judgment, as they become available. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2883 [...] [article] Closed-form fragility estimates, parameter sensitivity, and bayesian updating for RC columns [texte imprimé] / Do-Eun Choe, Auteur ; Gardoni, Paolo, Auteur ; Rosowsky, David, Auteur . - 2007 . - pp.833–843. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.833–843. Mots-clés : Bridges  Concrete  columns  Shear  Deformation  Bayesian  analysis  Sensitivity  analysis  Probabilistic  models  Parameters Résumé : Reinforced concrete (RC) columns are the most critical components in bridges under seismic excitation. In this paper, a simple closed-form formulation to estimate the fragility of RC columns is developed. The formulation is used to estimate the conditional probability of failure of an example column for given shear and deformation demands. The estimated fragilities are as accurate as more sophisticated estimates (i.e., predictive fragilities) and do not require any reliability software. A sensitivity analysis is carried out to identify to which parameter(s) the reliability of the example column is most sensitive. The closed-form formulation uses probabilistic capacity models. A Bayesian procedure is presented to update existing probabilistic models with new data. The model updating process can incorporate different types of information, including laboratory test data, field observations, and subjective engineering judgment, as they become available. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2883 [...]

Amplitude variability in simulated incoherent seismic ground motions1 / Dimitris Pachakis in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.844–848. Titre : Amplitude variability in simulated incoherent seismic ground motions1 Type de document : texte imprimé Auteurs : Dimitris Pachakis, Auteur ; Lambros S. Katafygiotis, Auteur ; Aspasia Zerva, Auteur Année de publication : 2007 Article en page(s) : pp.844–848. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Ground  motion  Simulation  models  Random  processes  Spectral  density  function  Spectral  analysis  Fourier  transform Résumé : This note compares in detail four commonly used schemes for the simulation of spatially variable ground motions. Emphasis is placed not only on the conformity of the simulations with the power and cross spectral density of the random field but, also, on the examination of the consistency of the simulations with the homogeneity condition, and the (Fourier) amplitude variability of the simulations. It is shown that, whereas three techniques that simulate ground motions in parallel satisfy the homogeneity requirement, produce simulations with random amplitudes, and amplitude and phase variability consistent with that of recorded data, one technique that simulates motions in sequence does not. ISSN : 0733-9399 En ligne : Ground motion, Simulation models, Random processes, Spectral density function, S [...] [article] Amplitude variability in simulated incoherent seismic ground motions1 [texte imprimé] / Dimitris Pachakis, Auteur ; Lambros S. Katafygiotis, Auteur ; Aspasia Zerva, Auteur . - 2007 . - pp.844–848. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.844–848. Mots-clés : Ground  motion  Simulation  models  Random  processes  Spectral  density  function  Spectral  analysis  Fourier  transform Résumé : This note compares in detail four commonly used schemes for the simulation of spatially variable ground motions. Emphasis is placed not only on the conformity of the simulations with the power and cross spectral density of the random field but, also, on the examination of the consistency of the simulations with the homogeneity condition, and the (Fourier) amplitude variability of the simulations. It is shown that, whereas three techniques that simulate ground motions in parallel satisfy the homogeneity requirement, produce simulations with random amplitudes, and amplitude and phase variability consistent with that of recorded data, one technique that simulates motions in sequence does not. ISSN : 0733-9399 En ligne : Ground motion, Simulation models, Random processes, Spectral density function, S [...]

Performance of wavelet transform and empirical mode decomposition in extracting signals embedded in noise / T. Kijewski-Correa in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.849–852. Titre : Performance of wavelet transform and empirical mode decomposition in extracting signals embedded in noise Type de document : texte imprimé Auteurs : T. Kijewski-Correa, Auteur ; Ahsan Kareem, Auteur Année de publication : 2007 Article en page(s) : pp.849–852. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Spectral  analysis  Stationary  processes,  Time  series  analysis  Frequency  analysis  Transformations  Noise  Transient  loads  Transient  response Résumé : Time-frequency transformations have gained increasing attention for the characterization of nonstationary signals in a broad spectrum of science and engineering applications. This study evaluates the performance of two popular transformations, the continuous wavelet transform and empirical mode decomposition with Hilbert transform (EMD+HT) , in estimating instantaneous frequency (IF) in the presence of noise. The findings demonstrate that under these conditions wavelets seeking harmonic similitude at various scales produce lower variance IF estimates than EMD+HT . The shortcomings of the latter approach are attributed to its empirical, envelope-dependent nature, leading to bases that are themselves derived from noise. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2884 [...] [article] Performance of wavelet transform and empirical mode decomposition in extracting signals embedded in noise [texte imprimé] / T. Kijewski-Correa, Auteur ; Ahsan Kareem, Auteur . - 2007 . - pp.849–852. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.849–852. Mots-clés : Spectral  analysis  Stationary  processes,  Time  series  analysis  Frequency  analysis  Transformations  Noise  Transient  loads  Transient  response Résumé : Time-frequency transformations have gained increasing attention for the characterization of nonstationary signals in a broad spectrum of science and engineering applications. This study evaluates the performance of two popular transformations, the continuous wavelet transform and empirical mode decomposition with Hilbert transform (EMD+HT) , in estimating instantaneous frequency (IF) in the presence of noise. The findings demonstrate that under these conditions wavelets seeking harmonic similitude at various scales produce lower variance IF estimates than EMD+HT . The shortcomings of the latter approach are attributed to its empirical, envelope-dependent nature, leading to bases that are themselves derived from noise. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2884 [...]

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